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Abstract:

A fuel measurement system for measuring a fuel consumption amount of an
engine, intended to reduce a measurement error of a Coriolis flowmeter to
thereby improve measurement accuracy and reproducibility of a fuel
consumption amount. The system includes: a Coriolis flowmeter provided on
a fuel supply path for supplying a fuel to the engine to measure a flow
rate of the fuel in the fuel supply path; and a temperature control
mechanism provided in an upstream side of the Coriolis flowmeter on the
fuel supply path to control a temperature of the fuel flowing into the
Coriolis flowmeter.

Claims:

1. A fuel measurement system for measuring a fuel consumed by an internal
combustion engine comprising: a Coriolis flowmeter provided on a fuel
supply path for supplying a fuel to the internal combustion engine to
measure a flow rate of the fuel in the fuel supply path; and a
temperature control mechanism provided in an upstream side of the
Coriolis flowmeter on the fuel supply path to control a temperature of
the fuel flowing into the Coriolis flowmeter.

2. The fuel measurement system according to claim 1, wherein the
temperature control mechanism comprises: a heat exchanger performing a
heat exchange between a cooling liquid flowing through a cooling liquid
flow path provided with a flow rate regulating valve and the fuel flowing
in the upstream side of the Coriolis flowmeter in the fuel supply path; a
temperature sensor provided inside the Coriolis flowmeter or in the
upstream side of the Coriolis flowmeter on the fuel supply path; and a
control unit adapted to control an opening degree of the flow rate
regulating valve using a detected temperature detected by the temperature
sensor to thereby control the flow rate of the cooling liquid flowing in
the heat exchanger.

3. The fuel measurement system according to claim 2 further comprising a
circulation flow path branched from a position between the heat exchanger
and the Coriolis flowmeter in the fuel supply path and joining to the
upstream side of the heat exchanger to form a circulation path in
association with the fuel supply path, wherein the heat exchanger is
provided between the branch point and the confluence of the circulation
flow path on the fuel supply path.

Description:

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to JP Application No. 2012-243111,
filed on Nov. 2, 2012, the disclosure of which is incorporated in its
entirety by reference herein.

TECHNICAL FIELD

[0002] The present invention relates to a fuel measurement system for
measuring a fuel consumed by an internal combustion engine.

BACKGROUND ART

[0003] As a conventional fuel measurement system, there has been
considered a measurement system for measuring a consumption amount of a
fuel consumed by an engine using a Coriolis flowmeter.

[0004] In this arrangement, since a Coriolis flowmeter can directly
measure a mass flow rate of the fuel without being affected by a
temperature and pressure of the fuel compared to other types of
flowmeters, a Coriolis flowmeter is increasingly used in a fuel
consumption amount measurement system in recent years.

[0005] However, in the case where the fuel is in a low flow rate region
such as a case of measuring a fuel consumption amount of an engine, for
example, in a state of idling, measurement values of the Coriolis
flowmeter are varied, and there arises a problem that reliability in
measuring a fuel consumption amount cannot be obtained.

[0006] As a cause of variation in measurement values of the Coriolis
flowmeter in a low flow rate region, there is considered a change in
elastic force of a pipe (flow tube) inside the Coriolis flowmeter due to
a temperature change of the fuel.

[0007] Although there is also a measurement system in which a temperature
correction of a measurement value is performed by a temperature sensor
provided inside a Coriolis flowmeter, this temperature correction is
performed using a default value (default value) and therefore the
correction accuracy may not be obtained sufficiently due to an
instrumental error of the Coriolis flowmeter in some cases.

[0008] An error due to the change in elastic force is in a degree of
0.0002 kg/h per 1° C. For example, in the case where a fuel of a
large flow rate in a degree of 100 kg/h is measured, since an error value
to a measurement value is extremely small, the error can be ignored.
Whereas, in the case where a fuel of a small flow rate in a degree of,
e.g., 10 kg/h is measured, the error value is large to a measurement
value and this error cannot be ignored from the viewpoint of measurement
accuracy.

[0009] It is noted that, although the configuration provided with the heat
exchanger in an upstream side of the Coriolis flowmeter in the system of
Japanese Patent JP2006-329990A, since the configuration is not provided
with a temperature sensor, this merely indicates that the fuel is cooled
in the upstream side of the Coriolis flowmeter.

SUMMARY OF INVENTION

Technical Problem

[0010] Therefore, the present invention has been made in order to solve
the problems at a stroke and its essential object is to reduce a
measurement error of a Coriolis flowmeter to thereby improve measurement
accuracy and reproducibility of a fuel consumption amount.

Solution to Problem

[0011] That is, a fuel measurement system according to the present
invention is intended to measure a fuel consumed by an internal
combustion engine, wherein the system includes: a Coriolis flowmeter
provided on a fuel supply path for supplying a fuel to the internal
combustion engine to measure a flow rate of the fuel in the fuel supply
path; and a temperature control mechanism provided in an upstream side of
the Coriolis flowmeter on the fuel supply path to control a temperature
of the fuel flowing into the Coriolis flowmeter.

[0012] With this configuration, since a mechanism for controlling a
temperature of the fuel flowing into the Coriolis flowmeter to be, for
example, constant is provided in the upstream side of the Coriolis
flowmeter, a measurement error due to a temperature change of the fuel in
the Coriolis flowmeter can be reduced. Thus, the measurement accuracy and
reproducibility of a fuel flow rate can be improved irrespective of a
flow rate range of the fuel or without depending on a temperature
correction using a temperature sensor and consequently the measurement
accuracy and reproducibility of a fuel consumption amount can be
improved.

[0013] As a specific configuration of the temperature control mechanism,
it is preferable that the temperature control mechanism includes: a heat
exchanger performing a heat exchange between a cooling liquid flowing
through a cooling liquid flow path provided with a flow rate regulating
valve and the fuel flowing in the upstream side of the Coriolis flowmeter
in the fuel supply path; a temperature sensor provided inside the
Coriolis flowmeter or in the upstream side of the Coriolis flowmeter on
the fuel supply path; and a control unit adapted to control an opening
degree of the flow rate regulating valve using a detected temperature
detected by the temperature sensor to thereby control the flow rate of
the cooling liquid flowing in the heat exchanger.

[0014] With this configuration, a valve opening degree of the flow rate
regulating valve can be feedback-controlled based on a deviation between
a target temperature of the fuel flowing into the Coriolis flowmeter and
a detection temperature detected by the temperature sensor and
consequently the temperature of the fuel flowing into the Coriolis
flowmeter can be controlled. At this time, in the case where the
temperature sensor is provided inside the Coriolis flowmeter, the
temperature of the fuel can be more accurately controlled to be a target
temperature constantly. Also, even in the case where the temperature
sensor is provided between the heat exchanger and the Coriolis flowmeter
in the fuel supply path, the temperature of the fuel can be more
accurately controlled to be a target temperature constantly.

[0015] It is preferable that the fuel measurement system further includes
a circulation flow path branched from a position between the heat
exchanger and the Coriolis flowmeter in the fuel supply path and joining
to the upstream side of the heat exchanger to form a circulation path in
association with the fuel supply path, wherein the heat exchanger is
provided between the branch point and the confluence of the circulation
flow path on the fuel supply path.

[0016] With this configuration, since the circulation path is formed by
the circulation flow path and the temperature-controlled fuel flowing in
the circulation flow path is mixed with the fuel prior to be
temperature-controlled, the temperature of the fuel can be easily kept
constant without depending only on ability of the heat exchanger. In
addition, since the heat exchanger is provided between the branch point
and the confluence of the circulation flow path and the flow rate in the
circulation path becomes large in this portion, the temperature of the
fuel can be easily made constant.

ADVANTAGEOUS EFFECTS OF INVENTION

[0017] According to the present invention configured as described above,
it becomes possible to reduce a measurement error accompanied by a
temperature change of the fuel in the Coriolis flowmeter by controlling a
temperature of the fuel flowing into the Coriolis flowmeter to be
constant, and therefore the measurement accuracy and reproducibility of
the fuel flow rate can be accordingly improved and consequently the
measurement accuracy and reproducibility of a fuel consumption amount
consumed by the internal combustion engine can be improved.

BRIEF DESCRIPTION OF DRAWINGS

[0018] FIG. 1 is a schematic diagram of a fuel consumption amount
measurement system of the present embodiment.

DESCRIPTION OF EMBODIMENTS

[0019] The following describes an embodiment of a fuel measurement system
according to the present invention referring to the accompanying
drawings.

[0020] A fuel measurement system 100 of the present embodiment is a fuel
consumption amount measurement system for measuring a consumption amount
of a fuel consumed by an engine E. As shown in FIG. 1, the fuel
consumption amount measurement system includes: a fuel supply path 2 for
supplying a fuel to the engine E; a Coriolis flowmeter 3 for measuring a
flow rate of the fuel flowing in the fuel supply path 2; and a
temperature control mechanism 4 for controlling a temperature of a fuel
flowing into the Coriolis flowmeter 3 to be constant. In this
arrangement, the fuel consumption amount measurement system 100 may
include calculating equipment (not shown) calculating a consumption
amount of a fuel consumed by the engine E based on a mass flow rate of
the fuel obtained by the Coriolis flowmeter 3. This calculating equipment
may be configured of a control unit 41 to be described later.

[0021] The fuel supply path 2 has its one end provided with a fuel
introduction port 21 and the other end connected to a fuel supply port El
of the engine E. In the fuel supply path 2, from the upstream side
thereof, there are provided the fuel introduction port 21, a first pump
P1 which is a conveying pump, a first heat exchanger HE1 for cooling the
fuel, the Coriolis flowmeter 3, a second pump P2 which is a suction pump,
a second heat exchanger HE2 for heating the fuel, a third heat exchanger
HE3 for cooling the fuel, and the like.

[0022] In the fuel supply path 2, a safety valve SV1 is provided in the
upstream side of the first pump Pl. This safety valve SV1 is adapted to
release a part of the fuel to the outside in order to reduce an inflow
pressure in the case where the fuel of a pressure equal to or higher than
a predetermined value, for example, equal to or higher than 250 kPa flows
in. Moreover, an air-bubble removing mechanism 5 for removing air bubbles
in the fuel is provided between the safety valve SV1 and the first pump
P1 in the fuel supply path 2. By this air-bubble removing mechanism 5,
air bubbles can be removed from the fuel immediately before the fuel
flows in the first pump P1.

[0023] The temperature control mechanism 4 includes the first heat
exchanger HE1, a fuel temperature sensor TS1 provided in the upstream
side of the Coriolis flowmeter 3 and a control unit 41 for controlling a
flow rate of cooling water serving as cooling liquid flowing through the
first heat exchanger HE1.

[0024] The first heat exchanger HE1 is adapted to perform heat exchange
between cooling water flowing through a first cooling liquid flow path 6
(referred to as "first cooling water flow path 6" hereinafter) which is
provided with a flow rate regulating valve CV1 and a fuel flowing in the
upstream side of the Coriolis flowmeter 3 on the fuel supply path 2. In
this arrangement, in the first cooling water flow path 6 for supplying
the cooling water to the first heat exchanger HE1, a third cooling water
flow path 7 is formed to be branched for supplying cooling water serving
as cooling liquid to the third heat exchanger HE3.

[0025] In the upstream side of the first heat exchanger HE1 in the first
cooling water flow path 6, a circulation pump P3 is provided for
circulating the cooling water. This circulation pump P3 is provided in
the upstream side of a branch point X1 of the third cooling water flow
path 7 in the first cooling water flow path 6 and has a function of not
only circulating the cooling water through the first cooling water flow
path 6 but also circulating the cooling water through the third cooling
water flow path 7. Further, in the upstream side of the circulation pump
P3 in the first cooling water flow path 6, a cooling water temperature
sensor TS2 is provided for detecting a temperature of the cooling water.
This cooling water temperature sensor TS2 is adapted to detect whether or
not the temperature of the cooling water flowing into the first and third
cooling water flow paths 6 and 7 is in a predetermined temperature range
(for example, in a range of 5° C. to 40° C.).

[0026] Moreover, in the downstream side of the first heat exchanger HE1 in
the first cooling water flow path 6, the flow rate regulating valve CV1
is provided for regulating the flow rate of the cooling water in the
first cooling water flow path 6. This flow rate regulating valve CV1 is
provided in the upstream side of a confluence X2 of the third cooling
water flow path 7 in the first cooling water flow path 6 and an opening
degree of the valve is controlled by the control unit 41 as to be
described later.

[0027] The fuel temperature sensor TS1 is provided between the first heat
exchanger HE1 and the Coriolis flowmeter 3 in the fuel supply path 2 so
as to detect a temperature of the fuel. It is noted here that the fuel
temperature sensor TS1 may be configured to detect a temperature of the
fuel by detecting a temperature of a pipe constituting the fuel supply
path 2, or may be configured to be provided inside the fuel supply path 2
so as to directly detect a temperature of the fuel.

[0028] The control unit 41 is configured of an exclusive and
general-purpose computer including a CPU, a memory, an AD converter and
the like and consequently the opening degree of the flow rate regulating
valve CV1 provided in the first cooling water flow path 6 is controlled
based on a temperature control program stored in an internal memory
thereof.

[0029] In specific, in the case where a detected temperature (temperature
of the fuel) obtained by the fuel temperature sensor TS1 is higher or
lower than a predetermined reference temperature, the control unit 41
controls the valve opening degree of the flow rate regulating valve CV1
so that the detected temperature obtained by the fuel temperature sensor
TS1 becomes the reference temperature. The control unit 41 performs the
temperature control of the fuel, for example, in a manner as follows.

[0030] (1) In the case where a detected temperature obtained by the fuel
temperature sensor TS1 is lower than the reference temperature, the
control unit 41 increases the valve opening degree of the flow rate
regulating valve CV 1 under the condition that the detected temperature
obtained by the fuel temperature sensor TS 1 is raised by increasing the
flow rate of the cooling water.

[0031] (2) In the case where the detected temperature obtained by the fuel
temperature sensor TS1 is lower than the reference temperature, the
control unit 41 decreases the valve opening degree of the flow rate
regulating valve CV1 under the condition that the detected temperature
obtained by the fuel temperature sensor TS1 is lowered by increasing the
flow rate of the cooling water.

[0032] (3) In the case where the detected temperature obtained by the fuel
temperature sensor TS1 is higher than the reference temperature, the
control unit 41 increases the valve opening degree of the flow rate
regulating valve CV1 under the condition that the detected temperature
obtained by the fuel temperature sensor TS1 is lowered by increasing the
flow rate of the cooling water.

[0033] (4) In the case where a detected temperature obtained by the fuel
temperature sensor TS1 is higher than the reference temperature, the
control unit 41 decreases the valve opening degree of the flow rate
regulating valve CV1 under the condition that the detected temperature
obtained by the fuel temperature sensor TS1 is raised by increasing the
flow rate of the cooling water.

[0034] Furthermore, the control unit 41 also controls a valve opening
degree of a flow rate regulating valve CV2 provided in the third cooling
water flow path 7 connected to a third heat exchanger HE3 based on a
detected temperature obtained by a temperature sensor TS3 provided in the
upstream side of the third heat exchanger HE3. Moreover, the control unit
41 acquires detection signals from a temperature sensor and pressure
sensor provided in the flow paths constituting the measurement system 100
and controls valves and pumps provided in these flow paths.

[0035] Furthermore, it may be considered that the predetermined reference
temperature is determined based on an ambient temperature. More
specifically, in the case where the ambient temperature is equal to or
lower than a predetermined temperature such as, e.g., 25 degrees, the
valve opening degree of the flow rate regulating valve CV1 is controlled
so that the temperature of the fuel becomes constant at the predetermined
temperature (i.e., 25 degrees) which is set as the reference temperature.
In the case where the ambient temperature is equal to or higher than a
predetermined temperature such as, e.g., 25 degrees, the valve opening
degree of the flow rate regulating valve CV1 is controlled so that the
temperature of the fuel becomes constant at the ambient temperature which
is used as the reference temperature.

[0036] A bypass path 8 which bypasses the first heat exchanger HE1 and the
flow rate regulating valve CV1 is provided between the upstream side of
the first heat exchanger HE1 (i.e., downstream side of the circulation
pump P3) in the first cooling water flow path 6 and the downstream side
of the first heat exchanger HE1 in the first cooling water flow path 6.
Specifically, the bypass path 8 is connected between, the upstream side
of the branch point X1 of the first cooling water flow path 6 and the
third cooling water flow path 7, and the downstream side of the
confluence X2 of the first cooling water flow path 6 and the third
cooling water flow path 7.

[0037] In this bypass path 8, there is provided a differential pressure
regulator 9 for maintaining a differential pressure between the upstream
side and downstream side of the first heat exchanger HE1 to be constant.
This differential pressure regulator 9 is adapted to release the cooling
water in the upstream side of the first cooling water flow path 6 to the
downstream side of the first heat exchanger HE1 through the bypass path 8
at the time of the pressure rising of the first cooling water flow path 6
which is caused in such a case where the flow rate regulating valve CV1
is closed.

[0038] In this fuel consumption amount measurement system 100, there is
provided a circulation flow path 10 for forming a circulation path R
which is branched from a point between the first heat exchanger HE1 and
the Coriolis flowmeter 3 in the fuel supply path 2 and joins with the
upstream side of the first heat exchanger HE1.

[0039] A pressure regulator PR1 is provided in this circulation flow path
10 to regulate the pressure of the fuel flowing in the circulation flow
path 10. The fuel temperature-controlled by the first heat exchanger HE1
flows in the circulation flow path 10 and this circulation flow path 10
configures that the temperature-controlled fuel is returned back to the
upstream side of the first heat exchanger HE1. Thus, since the
temperature-controlled fuel flowing in the circulation flow path 10 is
mixed with the fuel before the fuel is temperature-controlled, the
temperature of the fuel can be easily kept constant without relying only
on the ability of the first heat exchanger HE1.

[0040] In this circuit configuration of the circulation flow path 10, the
first heat exchanger HE1 and the first pump P1 are provided between the
branch point X3 and the confluence X4 of the circulation flow path 10 on
the fuel supply path 2. Thus, since the first heat exchanger HE1 and the
first pump P1 are provided in portions where the flow rate becomes large
in the circulation path R, the temperature of the fuel can be easily kept
constant.

[0041] Referring to other circuit configurations, the second heat
exchanger HE2 is adapted to heat the fuel controlled to be a constant
temperature by the first heat exchanger HE1 and to perform a heat
exchange between heating liquid (hot water) flowing through a heating
liquid flow path 11 and the fuel flowing through the fuel supply path 2.

[0042] Further, there is provided a fuel return path 12 for returning the
fuel remaining without being consumed by the engine E to the upstream
side of the second pump P2 on the fuel supply path 2. In specific, this
fuel return path 12 is connected between the downstream side of the
Coriolis flowmeter 3 and the upstream side of the second pump P2 in the
fuel supply path 2. A pressure regulator PR2 is provided between the
Coriolis flowmeter 3 and a connecting point X5 of the fuel return path
12, and the flow rate of the fuel flowing through the pressure regulator
PR2 corresponds to a consumption amount of the fuel consumed by the
engine E.

[0043] According to the fuel consumption amount measurement system 100
according to the present embodiment configured as described above, since
a mechanism for controlling the temperature of the fuel flowing into the
Coriolis flowmeter 3 to be constant is provided in the upstream side of
the Coriolis flowmeter 3, a measurement error due to a temperature change
of the fuel in the Coriolis flowmeter 3 can be reduced. Thus, the
measurement accuracy and reproducibility of a fuel consumption amount can
be improved even in a low flow rate region of the fuel without depending
on a temperature correction using a temperature sensor.

[0044] It is noted that the present invention should not be limited to the
above embodiment. For example, in the present embodiment, although the
fuel temperature sensor TS1 is provided between the first heat exchanger
HE1 and the Coriolis flowmeter 3 on the fuel supply path 2, the
temperature sensor provided in other location such as inside the Coriolis
flowmeter 3 may be used. In this case, it is not necessary to provide a
temperature sensor separately and the device configuration can be
simplified. Moreover, since the temperature of the pipe inside the
Coriolis flowmeter 3 is measured, the temperature of the fuel can be
controlled more accurately. In addition, it may be also configured such
that, considering an operating temperature of the first pump P1 as a
temperature of the fuel, the temperature of the fuel is controlled using
the operating temperature.

[0045] It may be also possible to reverse the arrangement of the first
heat exchanger HE1 and the first pump P1. Even in this case, it is
preferable that the first heat exchanger HE1 and the first pump P1 are
disposed between the branch point X3 and the confluence X4 of the
circulation flow path 10.

[0046] In addition, the present invention should not be limited to the
above embodiment, and various modifications are of course possible within
the scope unless departing from the intended spirit thereof.